Well, forget arbitrary short/medium/long bursts. Simply stated this table lets you determine, based on the gun's cyclic rate of fire, the maximum number of rounds that can come out of it in a given amount of game time. Remember a combat turn is 4 seconds long and contains up to 5 actions which I have arbitrarily named segments. Thus each segment is .8 seconds.

Think characters will want weapons with higher cyclic rates based on this? Possibly. We know that efforts were made by individuals & units in Vietnam to do the same thing with the weapons they were given so we're doing well because we're imitating real world events. There are drawbacks to a high ROF of course, faster ammo depletion being the most obvious. There are also controllability & accuracy issues, but that's getting into some complex areas.

This leads to interesting rules questions. If a character with a speed of 2 holds the trigger back on an M60 GPMG, does it fire only twice a turn or does it keep going even when the character can't take an action? That's a tricky one. I'll go into more detail about this and some related issues at a future date.